1. Field of the Invention
The invention pertains to the novel, relatively non-hygroscopic, crystalline .alpha.-form of the valuable hypotensive agent prazosin hydrochloride of the formula: ##STR1## AND PROCESSES FOR PREPARING SAID CRYSTALLINE .alpha.-FORM, AS WELL AS THE NOVEL, CRYSTALLINE POLYHYDRATE FORM OF PRAZOSIN HYDROCHLORIDE WHICH HAS A LOW, UNIFORM RATE OF DISSOLUTION.
2. Description of the Prior Art
U.S. Pat. Nos. 3,511,836, 3,635,979 and 3,663,706 disclose 2-[4-(2-furoyl)piperazin-1-yl]-4-amino-6,7-dimethoxyquinazoline. The first of these U.S. Patents specifically claims this compound and its acid addition salts and U.S. Pat. No. 3,663,706 claims the use of the compound and its pharmaceutically acceptable acid addition salts as valuable hypotensive agents. Pharmacological studies on 2-[4-(2-furoyl)piperazin-1-yl]-4-amino-6,7-dimethoxyquinazoline hydrochloride, hereinafter designated by its generic name, prazosin hydrochloride, were reported by Scriabine et al., Experientia, 24, 1150(1968), and by Constantine et al., in "Hypertension: Mechanisms and Management", Onesti et al., editors, Grune and Stratton, Inc., 1973, p. 429-444. Preliminary clinical studies on prazosin hydrochloride were reported by Cohen, J. Clin. Pharmacol., 10, 408(1970). Side effects due to initial doses of prazosin have been reported by Bendall et al., Brit. Med. Jour., 2, 727(1975).